loki/docs/sources/operations/caching.md

---
title: Caching 
menuTitle: Caching 
description: Enable and configure memcached for caching. 
weight: 100
keywords:
  - memcached
  - caching
---

# Caching

Loki supports caching of index writes and lookups, chunks and query results to
speed up query performance. This sections describes the recommended Memcached
configuration to enable caching for chunks and query results. The index lookup
cache is configured to be in-memory by default.

## Before you begin

- It is recommended to deploy four dedicated Memcached clusters.
- As of 2023-02-01, the `memcached:1.6.17-alpine` version of the library is recommended.
- Consult the Loki ksonnet [memcached](https://github.com/grafana/loki/blob/main/production/ksonnet/loki/memcached.libsonnet) deployment and the ksonnet [memcached library](https://github.com/grafana/jsonnet-libs/tree/master/memcached).

## Steps

To enable and configure Memcached:

1. Deploy each Memcached service with at least three replicas and configure
   each as follows:
    1. Chunk cache 
       ```
       --memory-limit=4096 --max-item-size=2m --conn-limit=1024
       ```
    1. Query result cache
       ```
       --memory-limit=1024 --max-item-size=5m --conn-limit=1024
       ```

1. Configure Loki to use the cache.
    1. If the Helm chart is used

       Set `memcached.chunk_cache.host` to the Memecache address for the chunk cache, `memcached.results_cache.host` to the Memecache address for the query result cache, `memcached.chunk_cache.enabled=true` and `memcached.results_cache.enabled=true`. 
       
       Ensure that the connection limit of Memcached is at least `number_of_clients * max_idle_conns`.
       
       The options `host` and `service` depend on the type of installation. For example, using the `bitname/memcached` Helm Charts with the following commands, the `service` values are always `memcached`.
       ```
       helm upgrade --install chunk-cache -n loki bitnami/memcached -f memcached-overrides.yaml
       helm upgrade --install write-cache -n loki bitnami/memcached -f memcached-overrides.yaml
       helm upgrade --install results-cache -n loki bitnami/memcached -f memcached-overrides.yaml
       helm upgrade --install index-cache -n loki bitnami/memcached -f memcached-overrides.yaml
       ```
       In this case, the Loki configuration would be
       ```yaml
       loki:
         memcached:
           chunk_cache:
             enabled: true
             host: chunk-cache-memcached.loki.svc
             service: memcache
             batch_size: 256
             parallelism: 10
           results_cache:
             enabled: true
             host: results-cache-memcached.loki.svc
             service: memcache
             default_validity: 12h
       ```
    1. If the Loki configuration is used
        1. Configure the chunk cache
           ```yaml
           chunk_store_config:
             chunk_cache_config:
               memcached:
                 batch_size: 256
                 parallelism: 10
               memcached_client:
                 host: <memcached host>
                 service: <port name of memcached service>
           ```
        1. Configure the query result cache
           ```yaml
           query_range:
             cache_results: true
             results_cache:
               cache:
                 memcached_client:
                   consistent_hash: true
                   host: <memcached host>
                   service: <port name of memcached service>
                   max_idle_conns: 16
                   timeout: 500ms
                   update_interval: 1m
           ```